On any weather map I've seen the arrow points in the direction of the wind and the little hockey stick ends are the speed. Long stick = 10 knots, short stick = 5 knots. So a hockey stick with two long and one short is 25 knots.

As noted by Ex-Calif, the numbers are the precise wind speed in knots, rather than in 5 knot increments as represented by the tails. Note that the tails do not represent the closest 5 knot increment (as I had assumed), but the next higher increment.

So 6-10 knots would be shown with a large tail, and 11-15 knots by a large tail and a small one.